Heating rods

ABSTRACT

The invention is concerned with heating rods which are arranged to be suspended in and to heat the water in an aquarium, the rods consisting of a heating coil embedded in an insulating material within an outer protected glass tube. According to the invention the lower end of the glass tube is open and is sealed by a stopper within a protected cap which acts to cushion impact between the lower end of the glass tube and an aquarium wall.

United States Patent [56] References Cited UNITED STATES PATENTS 1.951598 3/1934 Dearbom 338/241X 2.879.363 3/1959 Mucher 338/268X 3. 1 07,290 10/1963 Willinger 219/523X Primary Examiner-J. V. Truhe Assistant ExaminerC. L. Albritton Att0rneysCurt M. Avery, Arthur E. Wilfond, Herbert L Lerner and Daniel .1 Tick ABSTRACT: The invention is concerned with heating rods which are arranged to be suspended in and to heat the water in an aquarium, the rods consisting of a heating coil embedded in an insulating material within an outer protected glass tube. According to the invention the lower end of the glass tube is open and is sealed by a stopper within a protected cap which acts to cushion impact between the lower end of the glass tube and an aquarium wall.

FIG. 2

HEATING RODS The invention relates to a heating rod, particularly for heating the water in aquariums, of the kind consisting of a heating coil embedded in an insulating body, the whole enclosed in an outer protective glass tube.

In the known heating rods of this kind the protective glass tube has a closed bottom, somewhat after the manner of an ordinary test tube. However the manufacture of a glass tube closed at one end in this way is not only comparatively costly, but also has the disadvantage that the closed end of the tube always contains internal stresses in the glass, deriving from manufacture. it is therefore necessary to interpose a comparatively wide gap between the heating coil and the closed end of the glass tube, so as to reduce the temperature gradient here and so prevent the closed end of the tube from becoming excessively heated, which would involve a risk of the glass fracturing. Furthermore, the known glass heating rods are easily broken mechanically, for example by being struck against the wall of the aquarium during cleaning operations. if this happens the heating coil, which carries an electric current, can come into contact with the water in the aquarium, whereby the operator can be subjected to an electric shock, which can be fatal. I

The object of the present invention is to provide a heating rod of the kind described for heating the water in aquariums, less costly to manufacture than the known heating rods and protected against damage by mechanical shock. In accordance with the invention the part of the glass tube which is suspended downwards from the supporting wall does not merely hang down unprotected in the water, but its lower end is protected against inadvertant collision with the wall of the aquarium by the provision of an impact cushioning device inserted into or fitted over the lower end of the glass tube. For this purpose there could for example be used resilient rings, straps or the like mounted on the glass tube, in particular a suitably designed suction cup.

Preferably however the free end of the glass tube is protected from mechanical damage by means of a shock absorbing cap mounted on the end of the tube. The protective cap may contain a resilient stopper which is inserted in the open lower end of the glass tube to give a tight fit. This arrangement has the special advantage that the glass tube can be open at both ends, so that the comparatively costly closed end is no longer necessary. This eliminates the internal stresses in the glass which are always present when a glass tube with a closed end is used. The glass tube can be a plane glass tube, that is to say a section cut from an ordinary length of glass tubing. This considerably reduces the cost of the heating rod, and simplifies manufacture. 1

The resilient stopper may be mounted on a central pin of an outer protective cap, its lower surface resting in contact with a supporting flange in the outer protective cap. This arrangement ensures that the stopper makes a good seal, to prevent water from penetrating into the interior of the heating rod, where it might come into contact with the heating coil.

If the internal diameter of the peripheral wall of the protective cap is greater than the external diameter of the glass tube, an annular gap is left between the glass tube and the protective cap. In operation this gap is filled with water, effectively cooling the lower end of the glass tube. The arrangement also allows the glass tube to expand tenninally without hinderance.

The peripheral wall of the protective cap is preferably conically flared towards its upper rim. This arrangement provides excellent protection against mechanical damage, because if the heating rod collides with the aquarium wall the impact is taken by the wider upper rim of the cap, the rim making contact with the aquarium wall at one point only, giving the glass tube the greatest possible protection against mechanical damage.

One example of a heating rod constructed in accordance with the invention is illustrated in the accompanying drawings, in which:

FIG. 1 is a partly sectioned side view of the heating rod; and, FIG. 2 is a vertical section through the lower end of the heating rod, drawn to a larger scale.

In FIG. 1, the heating rod is closed at its upper end by an upper closure 2 through which pass electric leads 3 for a heating coil 4 situated in the interior of the heating rod 1. The heating coil 4 is embedded in an insulating ceramic jacket 5, which is itself contained in an outer protective glass tube 6. To prevent the ceramic jacket 5 from colliding with the glass tube 6, the space between these two parts can if desired be filled with sand. 7

' In operation, the heating rod is immersed in the water, suspended from a supporting wall, for example the wall of an aquarium. To prevent fracture of the glass tube 6 by collision with the aquarium wall, for example when the heating rod is being removed from the aquarium for cleaning the aquarium, the lower end of the glass tube 1 is protected by a cap 7, which is preferably made of a synthetic plastic material. From the bottom 8 of the cap 7 there projects upwards a supporting flange 9 and a central pin 10. A stopper ll, preferably made of rubber, is mounted on the central pin 10, the lower surface of the stopper resting on the supporting flange 9. ln assembling the heating rod the stopper 11 is first mounted in the protective cap 7, and is then pushed into the lower end of the glass tube 6. The stopper 11 is a close fit in the end of the glass tube 6, to prevent water from entering the interior of the heating rod, where it might otherwise come into contact with the heating coil 4 carrying electric current. The outer wall 12 of the protective cap 7 is conical, expanding towards the top, that is to say the upper rim of the protective cap has a greater diameter than the bottom. In the case of collision between the heating rod 1 and the aquarium wall, it is the upper rim of the cap which contacts the wall, effectively cushioning the impact.

As will be seen from FIG. 2, between the outer edge of the open bottom end of the glass tube 6 and the inner surface of the wall 12 of the cap there is an annular gap 13 which allows water to penetrate all the way down to the lower end of the glass tube, cooling this part of the glass tube. The annular gap 13 at the same time allows the glass tube 6 to expand without hinderance, that is to say without coming into contact with the wall 12 of the protective cap 7.

I claim:

1. A heating rod adapted to be suspended in and to heat the water in an aquarium, said rod comprising a body of insulating material, a heating coil embedded within said insulating material, an outer protective glass tube surrounding said insulating material and said heating coil embedded therein, and a protective cap mounted on said lower end of said glass tube a central pin projecting axially upwards in the interior of said cap and a central flange projects from the inner surface of the bottom of said cap, a stopper being mounted on said pin and supported by said flange to form a watertight seal.

2. A heating rod according to claim 1, wherein the internal diameter of said cap is greater than the external diameter of said glass tube.

3. A heating rod according to claim 2, wherein the peripheral wall of said cap is conically flared in the direction upwards from the bottom of said cap.

4. A heating rod according to claim 3, wherein said cap is made of a synthetic plastic material and said stopper is made of rubber. 

1. A heating rod adapted to be suspended in and to heat the water in an aquarium, said rod comprising a body of insulating material, a heating coil embedded within said insulating material, an outer protective glass tube surrounding said insulating material and said heating coil embedded therein, and a protective cap mounted on said lower end of said glass tube a central pin projecting axially upwArds in the interior of said cap and a central flange projects from the inner surface of the bottom of said cap, a stopper being mounted on said pin and supported by said flange to form a watertight seal.
 2. A heating rod according to claim 1, wherein the internal diameter of said cap is greater than the external diameter of said glass tube.
 3. A heating rod according to claim 2, wherein the peripheral wall of said cap is conically flared in the direction upwards from the bottom of said cap.
 4. A heating rod according to claim 3, wherein said cap is made of a synthetic plastic material and said stopper is made of rubber. 